Female Harmonia Axyridis (Harmonia Axyridis) Multiple Mating Fitness Study

Multiple mating can significantly improve the fitness of male insects, however, in theory only one or few times of mating would be sufficient for female insects to maintain the greatest reproductive success. In fact, multiple mating tends to bring female insects certain expenses such as loss of time, consumption of physical fitness, higher risk of exposure and being predated by natural enemies, increase in the risk of getting infectious diseases and parasites, and probably more physical injury. Nevertheless, there are still a large number of insects in nature choose to mate multiply, thus the study on the impacts of multiple mating on female insects, especially on the their fitness, would be necessary to explain the evolution of multiple mating for insects.Harmonia axyridis (Coleoptera:Coccinellidae), a typical multiple mating insect, is one of the most key species of ladybirds that has been widely used in biological control. In this study, the effects of multiple mating on the fitness of H.axyridis were examined by designing various mating frequency (single-mating group,4 mating groups,7 mating group,14 mating groups), and the results were as follows:1. The mating behaviors of H.axyridis include crawling back, inserting and insemination, and post-mating protection. The average mating duration was 157.62±20.43min, while it tended to extend as the increase of mating duration. Post-mating protection was a rotational behavior on the back of female insects after the completing of mating, and it lasted 4.63±1.30min. This behavior might be an evolutionary strategy caused by multiple mating for male H.axyridis to prevent re-mating of female with other male.2. H. axyridis started to spawn after the first mating till death, with average spawning quantities of 29.95±0.46 eggs per time, total quantities of 1063.04±62.15 eggs during the whole spawning cycle, and max quantity of 1683 eggs. The average weight of 10 eggs was 1.94±0.23mg. Multiple mating did not significantly affect weight of eggs.3. Multiple mating could increase the fitness of female H.axyridis. Multiple mating could stimulate female insects to enter spawning period. One week after mating, average spawning quantities of single mating group were 55.00±17.90 eggs, which were significantly less than multiple mating group (102.29±11.97 eggs,93.60±13.09 eggs,93.36±14.95 eggs, respectively). The average spawning quantities of multiple mating groups were 31.42±0.99,29.18±0.80 and 31.21±0.89 eggs, respectively, which were significantly more than single mating group (8.29±0.95 eggs). The average hatching rate in single mating group was 62.84±9.39%, while that in multiple mating group were 77.51±2.64%,88.71±0.29% and 82.27±2.58%, respectively. Multiple mating could significantly increase the average hatching rate of H.axyridis. The hatching rate in single mating group decreased 30 days after mating, while that in multiple mating group maintained stable, indicating that H.axyridis could restore sperm through multiple mating.4. The average life expectancies of H.axyridis were 53.33±3.12d, among which that of female insects in single mating group were 79.86±3.65d, and 56.71±6.91d,44.00±3.56d and 43.64±3.96d in 4,7,14 times mating groups, respectively. Mating time significantly affected the life expectancy of adult female H. axyridis, while the life expectancy decreased as the mating time increase.5. The hatching rate in 7 time mating group was the highest, suggesting the existence of the optimal number of mating for H. axyridis.